Anywhere from ~300-600 gph
. Ur tank is around 55 to 57 gallons. With the plants, u don't want to do 10x turnover. Around 5x turnover would be a place to start. It it is too much current, point the powerhead towards the glass and let it form a swirling current. I run 2 aqueon 55/75 on my 75 gallon with a biocube 250 and a aqueon 900 powerhead that I rarely run. I have rift cichlids so I don't need a lot of current.